Electrical combination lock and vehicle theft prevention system

ABSTRACT

A combination lock controlled by an electronic circuit that responds to actuation of selected ones of a bank of switches in predetermined order and is inhibited in response to actuation of any other one of the switches. The circuit includes an array of SCR&#39;&#39;s connected in series, each triggerable by actuation of a selected one of the switches. A solenoid is energized in response to firing of the last SCR in the array to open the lock. When used in an automobile to deter theft, the solenoid is preferably connected to control a valve in the fuel line, and includes a self-holding contact so that, once energized it remains energized until the ignition switch is turned off.

r 22] Filed:

United states Patent 1 Watson [54] ELECTRICAL COMBINATION LOCK AND VEHICLE THEFT PREVENTION SYSTEM [76] Inventor: 3 Donald Watson, 16 Stillmeadow Drive, Rochester, N.Y. 14624 May 21, 1971 21 Appl. No.: 145,744

[ May 1, 1973 3,380,024 4/1968 Watkinson ..317/134 X 3,500,751 3/1970 Robertson ..3 17/1 35 X 3,562,596 2/1971 Scheuer ..3l7/l34 3,309,542 3/1967 Elliot ..3l7/l54 X .Primary Examinerl-lenry T. Klinksiek Attorney-Hoffman Stone [57] ABSTRACT A combination lock controlled by an electronic circuit that responds to actuation of selected ones of a bank of switches in predetermined order and is inhibited in response to actuation of any other one of the switches. The circuit includes an array of SCRs connected in series, each triggerable by actuation of a selected one of the switches. A solenoid is energized in response to firing of the last SCR in the array to open the lock. When used in an automobile to deter theft, the soIenoid is preferably connected to control a valve in the fuel line, and includes a self-holding contact so that, once energized it remains energized until the ignition switch is turned off.

2 Ciaims, 1 Drawing Figure PATENIEDHAY '1 I973 INVENTOR. DONALD G. WATSON ATTORNEY ELECTRICAL COMBINATION LOCK AND VEHICLE THEFT PREVENTION SYSTEM BRIEF DESCRIPTION This invention relates to a novel, electricall.y controlled lock of the kind that responds to actuation of I selected ones of a bank of switches and is inhibited in will be found advantageous in many other utilizations.

It provides a simple and reliable combination arrangement, practically pick-proof, which can be readily adapted for use in almost any security system.

Briefly, the circuit of the invention includes a bank of momentary contact switches, typically ten in number,

The switches 8-1 to S- are connected to trigger the SCRs 20, 21, 22, and 24. The switches representing the predetermined code are connected respectively to trigger the enabling SCRs 20, 21, and 23. All of the other switches are commoned to the gate electrode of the inhibit SCR 24. The cathode of the first SCR 20 is grounded through the normally closed contact of a relay 26, which is energized in response to firing of the inhibit SCR 24. When the relay 26 is energized, the ground connection for all of the enabling SCRs 20, 21 and 22 is broken, and the enabling SCRs are held out off.

The solenoid valve 10 is connected in series with the last enabling SCR 22, and it is energized when that SCR fires. A self holding contact 28 is included in the soleand" an array of triggerable avalanche devices such as to be controlled is preferably a normally closed sole-- noid valve in the fuel line of the vehicle, and most of the circuit components are mounted, along with the valve, in a sturdy, weatherproof box beneath the floor of the vehicle.

DETAILED DESCRIPTION The presently preferred embodiment of the invention will now be described in connection with the accompanying drawing, wherein the single FIGURE is a schematic. diagram of a circuit according to the invention.

The circuit shown is arranged to control the operation of a solenoid valve in the fuel line 1 1 of an automobile. All of the components of the circuit included within the dashed rectangle 12 are preferably mounted in a weatherproof housing-secured beneath the floor of the automobile, where it is relatively inconspicuous and noid valve 10 to insure that, once energized, the valve 10 will remain energized and held open so long as the ignition switch 14 remains closed. This may be important at times because closure of one of the non-code switches will fire the inhibit SCR 24 and cut off the enabling SCRs 20, 21, and 22 at any time. Thus, if the self-holding contact 28 is omitted, the fuel supply might be cut off while the vehicle is in operation if one of the non-code switches were accidentally or inadvertently actuated. The contact 28 ensures against this.

The enabling SCRs 20, 21, and 22 are connected in series with each other, and only the first one 20 is directly grounded. They will, therefore, fire only in one-two-three sequence. Until the first SCR 20 fires, it holds the second one 21 cut off, and until the second one 21 fires, it holds the third one 22 cut off.

Only five wires are needed to connect the bank of switches S-l to S-0 and the battery 16 to the housing 12. All of the non-code switches may be commoned right at their terminals. With such an arrangement, however, a thief who knows'the operating principles of the circuit could cut the cable leading to the housing 12, and with the aid of an electrical meter fairly quickly identify the inhibit and battery leads. It would then be an easy matter to trigger the enabling SCRs 20 21, and 22, and make off with the vehicle. I

For maximum security, therefore, eleven leads are extended to the housing 12, one for the battery 16', and one for each of the switches S-l to S-0. Moreover, the switches are electrically isolated from each other by 1 diodes 30. With this arrangement, there is no way to inaccessible. Other devices such as, for example, the

starter relay may be electrically ganged with the solenoid valve 10 if desired, but it is believed that control of the fuel line alone provides adequate protectionagainst theft and that theadditional cost of supplementing it with starter, ignition, hood locks, or other controls is not ordinarily justifiable.

The circuit includes an array of ten momentary contact switches S-li through S-0, inclusive, which may be mounted on the instrument panel or steering column of the vehicle. The circuit as shown is arranged to energize the valve 10, opening it, in response to theactuation, in order, of three of the switches, S-8, S-2, and 8-5, representing the code combination 825. Actuation of any otherof the switches inhibits the circuit until the ignition switch 14 is opened.

The circuit is connected across the vehicles battery through .the ignition switch 14, and includes three SCRs 2'0, 21' and 22 connected in series with each other for energizingthe valve 10, and a fourth SCR 24 "for inhibiting the circuit.

distinguish by testing externally of the housing 12 between the code switches S-2, S5, and S-8, on the one hand, and the non-code switches, on the other. To foil the circuit, the would-be thief must either force entry into the housing 12, or be lucky enough to chance upon the predetermined code. I

For the same reason, the SCRs 20, 21, 22, and 24.

are preferably of the type conforming to U.S. military specifications Mil-S-l9500/l68 that are capable of stable and reliable operation without external connections between their trigger electrodes and their cathodes. SCRs commercially designated 2Nl770A, for example, are satisfactory for use in the circuit as shown. I

The circuit may be readily adapted for use in connection with any kind of lock system. Any desired electrically operatable device may be used in place of the solenoid valve 10. Also, in many utilizations, the selfholding contact 28 will not be needed because it is often desired to energize the controlled device only momentarily.

It should also be apparent that the code may include devices, whereby said avalanche devices may be fewer or more than the three digits illustratively fired by actuating said selected switches in a described herein. The circuit includes one SCR for predetermined order, each of the code digits, plus the inhibit SCR 24. e. means for inhibiting said avalanche devices in The circuit can also be readily modified for use in 5 response to actuation of any of said switches other systems where the positive battery terminal is grounded than Said lected Ones, and simply by reversing the polarity of the SCRs and the f. means for connecting the device to be controlled in diodes. series with the one of said avalanche devices trig- What is claimed is: gered by the selected switch that denotes the last 1 An electrical combination lock for energizing a digit Ofthe C d g device to be controlled comprisin 2. A combination lock according to claim 1 including a. triggerable avalanche devices equal in number to a Sturdy housing for avalanche device? and the th number f di i i a predetermined code device to be controlled, a separate panel spaced from bination, said avalanche devices being connected Said housing for mounting the Switches, and a i ie i h h other d i the device to be conductor cable for connecting the switches to the I controlled, avalanche devices, said cable including a separate coni), an array f switches greater in number than Said ductor for each of said switches, and isolating means in avalanche devices, I said housing for electrically isolating said separate conmeans f Connecting Said switches and Said ductors from each other, whereby electrical testing exavaianche devices to a current Source ternally of said housing is ineffective to distinguish d Selected Ones f Said Switches being arranged to between said selected and said other switches.

trigger different respective ones of said avalanche 

1. An electrical combination lock for energizing a device to be controlled comprising: a. triggerable avalanche devices equal in number to the number of digits in a predetermined code combination, said avalanche devices being connected in series with each other and with the device to be controlled, b. an array of switches greater in number than said avalanche devices, c. means for connecting said switches and said avalanche devices to a current source, d. selected ones of said switches being arranged to trigger different respective ones of said avalanche devices, whereby said avalanche devices may be fired by actuating said selected switches in a predetermined order, e. means for inhibiting said avalanche devices in response to actuation of any of said switches other than said selected ones, and f. means for connecting the device to be controlled in series with the one of said avalanche devices triggered by the selected switch that denotes the last digit of the code.
 2. A combination lock according to claim 1 including a sturdy housing for the avalanche devices and the device to be controlled, a separate panel spaced from said housing for mounting the switches, and a multi-conductor cable for connecting the switches to the avalanche devices, said cable including a separate conductor for each of said switches, and isolating means in said housing for electrically isolating said separate conductors from each other, whereby electrical testing externally of said housing is ineffective to distinguish between said selected and said other switches. 